Thermostatic circuit closer



Deg, 9,, 1924.

N. H. FREEMAN THERMOSTATIC CIRCUIT CLOSER Filed Sept. 2, 1921 PatentedDec. 9, 1924.-

UNITED STATES PATENT OFFICE.

NAT HARRIS FREEMAN, OF HOLBORN, LONDON, ENGLAND.

THERMOSTATIC CIRCUIT CLOSER.

Application filed September 2, 1921.

To all whom it may concern Be it known that I, NAT HARRIS FREEMAN, acitizen of the United States of America, residing at Holborn, London,England, have invented certain new and useful Improvements inThermostatic Circuit Closers, of which the following is a specification.

This invention relates to thermostatic cir cuit closers which areparticularly adapted for use with furnace chambers and other apparatus,such as fire-alarms, and has for one of its objects to provide animproved construction which shall be less liable to derangement duringworking than those known heretofore. Another object of the invention isto extend the range of temperature which can be controlled by suchdevices.

The thermostatic circuit closer according to the present invention is ofthe type which comprises a holder for fluid (hereinafter termed a gasholder) which holder is intended to be placed in the chamber whereof thetemperature is to be controlled, and a conduit extending from d holderto one surface of a movable opera mg -member, such as a column ofmercury, which member is exposed at another surface to atmosphericpressure, and is movable under the pressure ofsaid fluid into and out ofoperative position to close and open an electric circuit. Such a circuitcloser is described in the specification of my United Statesspecification Serial No. 442,195, and the present invention mayconveniently,though not essentially, be used in conjunction with thefeatures of that specification.

- According to the primary feature of the present invention there isprovided a thermostatic circuit closer of the type above described whichis characterized by the provision of an automatic pressure-operatedvalve which is distinct from said movable member and is arranged tocontrol communications between the interior of said holder and theexterior thereof. Conveniently the valve is arranged to operate eitherto admit fluid to the holder or to release fluid from the holderaccording to the variations in the relative pressure in the interior andat the exterior thereof. By the provision of such a valve, safety valveaction can be secured whereby derangement of the a paratus in abnormalcircumstances may e prevented. This safety valve action is more fullydescribed hereinafter.

Serial No. 498,163.

According to another feature of the invention a temperature controllingdevice is provided which, instead of operating to close the circuit at aconstant temperature of the fluid in the holder, is arranged to providefor a series of predetermined temperatures each higher than thepreceding one. In this case the valve is combined with adjusting meanswhereby it can be set to open momentarily, during the cyles oftemperature changes in the normal working of the device, at some instantin the increase of temperature (namely the expansion) of the fluid inthe holder between that instant in a cycle at which the temperature issuch that the movable operating member first reaches operative positionand that instant at which the temperature reaches its maximum for suchcycle (namely the instant of maximum expansion of the fluid in theholder).

The invention also comprises the provision of a temperature controllingdevice which is arranged to provide for a series of predeterminedtemperatures each lower than the preceding one. For this purpose thevalve is combined with adjusting means whereby it can beset to openmomentarily, during the cycles of temperature changes in the normalworking of the device, at some instant in the decrease of temperature(namely the contraction) of the fluid in the holder between that instantin a cycle at which the temperature is such that the pressures insideand outside of the holder are equal, and that instant at which thetemperature reaches its minimum for such cycle (namely the instant ofmaximum contraction of the fluid in the holder).

Preferably the valve is combined with adjusting means whereby it can beset to open at abnormal increase and abnormal decrease in pressure inthe holder, and also momentarily, during normal working of the device,at either of the instants specified in the two preceding paragraphs.

For a more complete understanding of the invention there will now bedescribed, by

way of example only and with reference to the accompanying drawings,certain constructional forms of thermostatic circuit closers accordin tothe invention. It is to be understo however, that the invention is notlimited to the precise details set forth.

In these drawings Figure 1 is an elevation, partly in section,

(lit

showing more or less diagrammatically one form of the present .inventionas applied to an apparatus of the kind described in the aforesaid priorpatent specification.

Figure 2 is a detail view of a modification of part thereof.

Figure 3 is a similar view of another modification, and

Figure 4 a view on a larger scale of a further modification.

Like reference numerals indicate like parts throughout the drawings.

In the construction illustrated the valve takes the form of a liquidseal to the open end of the conduit which communicates with the holder11 for fluid, and preferably the volumetric capacity of the conduit 10is such that there can be drawn into it, andv it will contain, asulficient quantity of the sealing liquid 12 to expose the. open end ofthe conduit to atmosphere. The holder 11 may take the form of a gas bulbwhich is to be' inserted in the chamber whereof the temperature is to becontrolled, and is shown as connected by a tube 13 to a column ofmercury 14 contained in an angularly adjustable tube 19 whichcommunicates with the tube 13 by a conduit as described in the aforesaidprior patent specification. The mercury co-operates with an adjustablecontact 21, as described in the said prior specification, to open andclose an'electri'c circuit including the mercury column 14, thecontact-wire 21, the supports carrying the same and the wires 22 and 23connected to these supports. Opening from the tube 13 there is shown abranch tube 15 which communicates with the conduit 10. The sealingliquid is received in a container 16 and the position of the latter canbe adjusted by the screw 17 to immerse the open end of the tube 10 moreor less below the surface of the sealing liquid 12. Included in thebranch 15 there may be one or more enlargements 18 to receive sealingliquid sucked into the tube 10 and thus prevent the said liquid fromreaching the main conduit 13.

Usually the holder 11 will contain air and bubles of air will passbetween the holder 11 and atmosphere via the tube 10. Other gases orliquids may, however, be employed provided that the sealing liquid issuitably chosen to correspond and that a correspondlng atmosphere isprovided between which and the holder 1'1 the bubbles may pass. Anysuitable liquid may be used for the seal but it should be such as not toevaporate quickly nor to affect adversely the fluid in the holder.

Safety val 0e a0ti0n.-For a simple safety valve action the apparatusshould be so set that on the circuit being closed no bubbles will passinto or out of the holder 11. Should, however, the air in the holderexpand excessively the tendency, if the safety valve were not present,would be for the mercury to be blown out of its tube 19. Instead of thisoccurring, however, the excess pressure of air is got rid of by allowingbu bles of air to pass out through the sealing liquid 12. The mercury,therefore, will not be unduly displaced from itscorrect operativeposition. If, on the other hand, the air in the holder should undulycontract the tendency, in the absence of the safety-valve, would be forthe mercury to be sucked back into the tube 13, whence it would be verydifficult to displace it again. But instead of this happening thesealing liquid 12 is sucked up into or toward the enlargements 1'8whence it is easily displaced later.

Temperature in0rease.'It will be appre ciated that the mercury does notimmediately discontinue its outward movement at the instant that ittouches the contact 21, but due partly perhaps to a little momentumwhich it has ac uired, but mainly to the expansion of t e air in theholder 11 'and the adjacent tubes, it moves along the contact and thuscauses the point of the latter to be immersed to a greater or lesserextent.

For some purposes, for example pottery work, it is desirable thatinstead of the tem perature in the chamber under control beingmaintained constant, it should be caused to increase gradually and undercontrol at a predetermined rate. For this purpose the apparatus shouldbe so set by adjusting the height of the level of the sealing liquid 12in relation to the open end of the tube 10 that at some instant betweenthat at which the mercury first touches the contact 21 and the instantof maximum expansion, a bubble of air is released from the tube 10.After the bubble is released there will naturally be less air in theholder 11 and its tubes than before, and for any given temperature the.

. 10 than before, to an extent governed ,by its specific gravity. If,however, heat is continued to be supplied, the air in the holder 11 andits tubes will ultimately reach such a temperature as to cause it toattain a pressure and volume sufiicient to cause the mercury to reachand pass beyond the contact 21 and also release another bubble. Since asmaller quantity of air is in question, however, than at first, thetemperature required to effect this will be higher than before, and thusinstead of the apparatus securing a constant temperature it will 0 crateto secure a governed but continuous y increasing temperature. The rateof increase will depend upon the size of the bubble released, and thiscan be governed by varying the specific gravity of the sealing liquid12, or by varying the aperture through which the bubble is released, sayby perforated concentric sleeves upon the tube 10, or other means.

Insetting the apparatus, care should be taken that it is not so arrangedthat a bubble is released suiflciently early during the expansion of theair to prevent the mercury from reaching the contact 21. If this occursat the first expansion of the air, it will in all probability occurduring succeeding expansions, with the result that the mercury willnever reach the contact and thus the supply of heat will never beautomatically shut oil'. In other words such a setting of the valve cutsout of operation entirely the temperature controlling device.

Temperature decrease-To cause the temperature to decrease gradually andunder control at a predetermined rate, the apparatus should be so setthat at some instant between that at which the pressures inside andoutside the holder 11' are equal and the instant of maximum contraction,a bubble of air is admitted from atmosphere to the holder. The operationis the converse of that hereinbefore described in connection withsecuring temperature increase.

Any suitable bubble-forming device may be employed. The tube has a plainopen end in the construction shown in Figure 1. In the constructionshown in Figure 2 a slit 24 is provided for formin the bubble, while inthe construction shown in Figure 3 the tube 10 has a bell mouth. In theconstruction shown in Figure 4, the tube 10 has a slit 2% the operativeopening of which is controlled by a sleeve 26 which is perforated at 27.The sleeve 26 can be rotated upon the tube 10 to shut ofl' more or lessof the length of the slit 24 as desired. The sleeve 26 may convenientlybe held in place by splaying the end of the tube 10 after the sleeve hasbeen placed in position.

What I claim as my invention and desire to secure by Letters Patentis 1. A thermostatic circuit closer comprising a holder for fluidadapted to be placed in. a chamber, the temperature of which is to becontrolled, an electrical circuit-closing device comprising a movablecolumn of electrically conducting material controlled by the pressure ofthe fluid in said holder, and an automatic pressure-operated valvedistinct from said movablecolumn and arranged to control communicationbetween the interior of said holder and the exterior thereof. n I

2. A thermostatic circuit closer comprising a holder for fluid, adaptedto be placed in a chamber, the temperature of which is to be controlled,and an electrical circuit-closing device comprising a movable column ofelectrically conducting material controlled by the pressure of the fluidin said holder, and an automatlc valve distinct from said devicecomprising a tubular container carrying a movable column of electricallyconducting material, a conduit connecting the lower end of saldcontainer with said holder,

and an automatic valve which is distinct from said movable column, isoperated by pressure in said holder and is arranged to controlcommunication between the interior of said conduit and the atmosphere.

4. A thermostatic circuit closer comprising a holder for fluid adaptedto be placed in a chamber, the temperature of which is to be controlled,an electrical circuit-closing device comprising a movable column ofelectrically conducting material controlled by the pressure of the fluidin said holder, an automatic valve operated by the fluid pressure in theholder and arranged to control communication between the interior andthe exterior of said holder, and means for adjusting said valve topermit the same to open momentarily owing to increase of pressure on itdue to increase of temperature of the fluid in the holder at someinstant between that instant in a cycle of temperature changes at whichthe temperature is such that the movable column first reaches operativeposition and that instant at which the temperature reaches its maximumfor such cycle.

5. A thermostatic circuit closer comprising a holder for fluid adaptedto be'placed in a chamber, the temperature'of which is to be controlled,an electrical circuit-closing device comprising a movable column of anelectrically conducting material controlled by the pressure of the fluidin said holder, an automatic valve operated by the fluid pressure in theholder and arranged to control communication between the interior andthe exterior of said holder, and means for adjusting said valve topermit the same to open momentarily owing to decrease of pres sure on itdue to decrease of temperature of the fluid in the holder, at someinstant between that instant in a cycle of temperature changes at whichthe temperature is such that the pressures inside and outside of theholder are equal, and that instant at which the temperature reaches itsminimum for such cycle, namely, the instant of maximum contraction ofthe fluid in the holder.

6. A thermostatic circuit closer comprising a holder for fluid adaptedto be placed in imum and minimum pressures.

7. A thermostatic circuit closer comprising a holder for fluid adaptedto be placed in a chamber, the temperature of which is to be controlled,and an electrical circuit- ,closing device comprising a movable columnof electrically conducting material controlled by the pressure of thefluid in said holder and an automatic valve operated by the fluidpressure in said holder and arranged to control communication betweenthe interior and the exterior of said holder, said valve distinct fromsaid movable column and taking the form of a liquid seal at the open endof a'conduit communicating with said holder.

8. A thermostatic circuit closer comprising a holder for fluid adaptedto be placed in a chamber, the temperature of which is .to becontrolled, an electrical circuit-closing device comprising a tubularcontainer carrying a movable column of electrically conducting material,and a conduit connecting the lower end of said container with saidholder, a valve conduit opening into the aforesaid conduit, and a liquidseal distinct vfrom said movable column for the open end of'said valveconduit.

9. A thermostatic circuit closer comprisring "a holder for fluid adaptedto be placed in a chamber, the temperature of which is to be controlled,an electrical circuit-closing devlce comprising a tubular containercarrying a movable column of electrically conducting material, a conduitconnecting the lower endof said container with said holder, a valveconduit opening into the aforesaid conduit, and a liquid seal for theopen end of said valve conduit, the 0 en end of said valve conduithaving a bubb e-forming slit.

10. A thermostatic circuit closer comprising a holder for fluid, adaptedto be placed in a chamber, the temperature of which is to be controlled,an electrical circuit-closing device comprising a tubular container anda movable column of electrically conducting material therein, a conduitconnecting the lower end of said container with said holder, a valveconduit opening at one end into the aforesaid conduit and having abubble-forming slit at its other end, a liquid seal for the slit end ofsaid valve conduit, and means for adjusting the operative area of saidslit.

11. A thermostatic circuit closer comprising a holder for fluid adaptedto be placed in a chamber, the temperature of which is to be controlled,an electrical circuit-closing device comprising a movable column ofelectrically conducting material controlled by the pressure of the fluidin said holder, an automatic valve operated by the pressure in saidholder and arranged to control communication between the interior of theholder and the atmosphere, a valve conduit in open communication at oneend with said holder, and a liquid seal for the other end of said valveconduit, said liquid-sealed conduit comprising a chamber of such volumetric capacity that it can contain a sufficient quantity of the sealingliquidrto expose the open end of the valve conduit to atmosphere andthereby connect the said holder with atmosphere.

Intestimony whereof I aflix my signature.

NAT HARRIS FREEMAN

